Osama Bin Laden Dead: U.S. Law Enforcement on 'Tip-Toe' Status to Stop Retaliation

FBI and other agencies on guard against al Qaeda, in U.S. and abroad.

May 4, 2011 -- The United States is pulling out all the stops to try to detect and head off any plots to avenge the death of Osama bin Laden, top counterterrorism officials said, calling this a dangerous moment.

FBI and Homeland Security officials are on "tip-toe" status, reviewing all intelligence and aggressively pushing informants in an effort to thwart any possible retaliatory attack. Attorney General Eric Holder said he has ordered U.S. Attorney Offices across the country, and counterterrorism investigators, to review investigative files and cases because of concerns of retaliatory attacks.

"I think we will ultimately be more safe as a result of his death," Holder said Wednesday on Capitol Hill. "But in the short term, we have some serious concerns we have to be ready to address."

When asked by Sen. Chuck Schumer, D-N.Y., whether the material seized at bin Laden's compound would lead to individuals being added to the terrorist and no-fly watch lists, Holder said, "The material that was seized will be reviewed by an interagency team, CIA, Justice, other intelligence agencies and other law enforcement agencies are all contributing people and machines. ... As we glean information from that material we will make appropriate determinations about who would be added to the watch list and no-fly list.

"We cannot become complacent, the fight is far from over," Holder said, noting that he ordered "prosecutors and law enforcement agencies to be mindful that bin Laden's death could result in retaliatory attacks in the U.S. or against our interests overseas.

"I've instructed department officials and our state and local officials to maintain focus on our counterterrorism efforts," he said.

See all of ABC's coverage of the death of Osama bin Laden.

The FBI held a conference call with all field offices to review and ramp up its existing terrorism cases. The order from headquarters was to check in with informants and tighten up case files and run down any potential leads, according to sources. In order to personally oversee the effort, FBI Director Robert Mueller cancelled a trip overseas this week, and is staying in Washington.

One former top counterterrorism official said the biggest threat right now might come from a "lone wolf" terrorist here in the United States, a true believer who is motivated to avenge Bin Laden.

"You're not going to have 19 hijackers taking down aircraft," Philip Mudd said, "but kids trying to find AK-47s or buy handguns or hand grenades on the street and go do something at a commercial facility like a mall or a 7-11."

Mudd was the deputy director of counterterrorism at the CIA before moving to the FBI to become the senior intelligence adviser to the FBI until he left the government in 2010. Rather than celebrating the death of bin Laden, Midd said, counterterrorism operatives realize this is "an urgent time" and are focused on "who is coming at us."

The one group that is being watched most closely, he said, is al Qaeda in the Arabian Peninsula. The Yemen-based group was responsible for smuggling package bombs on cargo planes headed to the United States last fall, and the attempt to bomb a U.S. passenger plane Christmas Day 2009.

Mudd predicted that its leader, radical cleric Anwar al-Awalki, will "redouble his efforts to get on the scoreboard. I think he will be looking around saying, what can we do quickly."

In addition, all officials at the Department of Homeland Security, including Immigration and Customs Enforcement and Border Protection agents, have been ordered to review their cases and be extra-vigilant.

Officials say part of the goal is to send the message to any potential terrorists that the United States is on high alert, and any efforts to retaliate for bin Laden's death would meet with failure.